The present invention relates generally to a control valve, and more specifically to a double valve constructed from two unitary valve assemblies.
Pneumatically powered machine tools operate through a valve system which interacts with a pneumatically controlled clutch and/or a brake assembly. For safety reasons, control valves that operate the machine tools require the operator to simultaneously activate two separate control switches to ensure that the operator's hands are away from moving components of the machine tool when initiating an operating cycle. An electronic circuit responsive to the two control switches generates a pilot control signal applied to solenoid pilot valves to control delivery of a fluid through the valve system to the machine tool.
In a typical 3-2 normally closed double valve, two movable valve assemblies are mounted within respective bores within a single valve body. This is in contrast, for example, to a 3-2 normally open valve. To achieve a normally-open function rather than a normally-closed function, the input and output pressures cannot simply be swapped. Rather, the current state of the art is to use two separate valve assemblies in a particular configuration to otherwise achieve a 3-2 normally open function. In one prior double valve, the solenoid pilot valves are moved to an actuated position in response to an electrical control signal from a respective operator-controlled switch, which allows fluid to flow through a single outlet passage of the double valve. If a valve assembly does not deactuate or actuate properly, or if the solenoid pilot valves are actuated or deactuated non-simultaneously, the double valve can malfunction. As the double valve includes a single outlet passage, the fluid can only be directed to a single location.